=[r"dm+[d-dm-2r ddm =Jo+md-2d.「rdm 1 [rdm=-[(xi+x m ∴J=Jc+md2 -平行轴定理   = + −  m m m r dm d dm r ddm   2 2 2  = + −  m JC md d rdm  2 2   = + m m xi yj dm m rdm m ( ) 1  1    = 0 2 J = J C + md -平行轴定理 ydmj m xdmi m m m     = + 1 1